Process for desulphurizing hydrocarbons



Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE PROCESS FOR DESULPHURIZING HYDROOARBONS Albert E. Buell and Walter A. Schuize, Bartiesville, kla., assignors to Phillips Petroleum Company, Bartlesville, 0kla., a corporation of Delaware 7 Claims.'

This application is a division of our co-pending application, Serial No. 616,574, filed June 10, 1932, entitled Processes for desulphurizing hydrocarbons, wherein it is shown that certain minerals constitute effective contact agents for the vapor phase desulphurization of hydrocarbons by which a part, of the organically combined sulphur is.

eliminated as hydrogen sulphide.

This invention relates to processes for treating sulphur bearing hydrocarbon mixtures such as natural or refinery gases, the naphtha derived from. the distillation or cracking of petroleum, oil

shale distillates, and other hydrocarbon products from which the removal of certain sulphur com- 1 pounds is desired.

More specifically it relates to the partial desulphurization of straight run and cracked gasolines, to which the process is particularly applicable, and the following disclosure will be limited to this application of the process for the sake of 30 ity of product, as well as of excessive cost.

To overcomethese objections, processes have been devised for sulphur removal which are based on the known catalytic action of certain contact agents on sulphur compounds in the vapor phase 5 at elevated temperatures, in which the sulphur is eliminated as hydrogen sulphide. The present invention is an improvement of processes of this type, particularly with respect to the nature and preparation of the contact agents employed.

40 The catalysts proposed by previous investigators are metals, or oxides or sulphides of metals. Metals known to be hydrogenation catalysts have a limited usefulness in a. process primarily employed to eliminate sulphur rather than to obtain 45 hydrogenation efiects, because of their ability to cause rapid decomposition of hydrocarbons under the operating conditions with accompanying deposition of carbonaceous residues and consequent poisoning of the catalyst. Therefore, metallic 50 sulphides, oxides, or oxides convertible to sulphides during the desulphurization process are advantageously employed, as their action is more exclusively confined to the sulphur impurities in the hydrocarbons.

. The oxides and sulphides mentioned, which are used in desulphurization processes, are at present synthetically prepared as more or less pure compounds, and are often deposited upon or admixed with more or less inactive carriers. The use and preparation of these synthetic substances is un- 5 duly expensive, and such catalysts usually have no salvage value when their usefulness as contact agents has been outlived. Undoubtedly it is for these reasons that the general adoption of catalytic desulphurization processes, the principles of 10 which have been long and widely known, has been so unduly delayed. Another disadvantage of the synthetically prepared agents is that their usual form is a. finely precipitated powder, which is inconvenient to handle, diflicult to maintain in a 15 reaction chamber thru which gases are moving at a high velocity, and which tends to pack and produce a high back pressure if it cannot be incorporated in a suitable carrier.

The primary object of this invention is to provide a novel catalyst for use in processes for desulphurizing hydrocarbons containing organic sulphur compounds as impurities, the sulphur being eliminated in the form of hydrogen sulphide, which catalyst overcomes the several objections, previously enumerated, to the specially. prepared catalysts used by previous investigators.

We have found that certain naturally occurring substances, containing compounds of the class mentioned above as contact agents, may be used substantially in their original state as catalysts.

These substances are relatively inexpensive compared to the corresponding synthetic compound. Moreover, their natural form is in many ways superior to the synthetic form, as the natural crystals or lumps of these substances may be easily reduced by crushing to a convenient and efiicient size for contact purposes as contrasted with the powdery form of the synthetic compound. Furthermore, the natural substance is often as eflicient, or even more so (in proportion to the percentage of active element present) as the prepared agent.

The naturally occurring substances referred to are metallic minerals or ores of these minerals which consist of oxides and sulphides of the metals whose oxides are grouped as dehydration and dehydrogenation catalysts, e. g., aluminum, tungsten, vanadium, chromium, cadmium, zinc, molybdenum, etc. Examples of these minerals are chromite, vanadinite, molybdenite, molybdite, descloizite, wolframite, bauxite, etc.

Temperatures of the order of BOO-800 F, are usually necessary, depending on (1) the particular mineral used as catalyst, 2) the time of contact between the petroleum product and the catalytic material, and (3) the specific properties of the hydrocarbon vapor which is being desulphurized. Temperatures of GOO-700 F. are usually preferred when straight run naphthas or cracked distillates are the products undergoing treatment. High pressures are not needed, extremely good results being obtained at atmospheric pressure. In practice it is usually desired to use pressures somewhat above atmospheric so that the vapors can be directly conducted to a fractionator or to treating tanks for final processing.

This conversion of the organic sulphur compounds to hydrogen sulphide may be accompanied by dehydrogenation of some of the hydrocarbons present, depending on the particular catalyst and the temperature used.

The presence of hydrogen gas in the sulphur bearing petroleum vapor aids in the conversion of the sulphur compounds to hydrogen sulphide when certain of the minerals, for example, vanadinite; are used as catalysts. Hydrogen sulphide (in small quantities) and inert gases along with the petroleum vapor apparently make little difference in the amount of desulphurization which can be obtained in one passage over the mineral I catalyst.

A typical process for desulphurization of cracked gasoline consists in passing the superheated vapors thru a bed of catalytic material maintained at an elevated temperature, say 700 F.', which eliminates a part or all the sulphur from mercaptans, alkyl sulphides, etc., as hydro-- catalyst comprising a crushed ore (30-60 mesh) containing the minerals vanadinite and descloizite at a temperature of 700 -F. and. at a rate such that the contact time was about two seconds. The resulting product was sweet, indicating that the mercaptans present had been completely converted, and had a sulphur content The same catalyst also effected a reduction of sulphur content of from 0.091% to 0.034% and completely sweetened a sour straight run naphtha at the same temperature and flow rate.

Example II.-Chromite crushed to 30-60 mesh and maintained'at a temperature of 700 F. was used as the catalyst. Vapors of a sour straight run naphtha were passed over at a rate to produce a contact time of about two seconds with an effect identical to that described in the previous example; Prolonged passage of this product over the catalyst failed to produce 'an appreciable change in its activity. In the next run over the same catalyst, 10% by volume of butyl mercaptan was added to the naphtha. The enormous sulphur content of this product was completely converted to hydrogen sulphide, as shown by test ing the condensate with cadmium sulphate solution.- After this severe abuse of the catalyst, it

was no longer able at the same flow rate, to produce a completely sweet product, but was still capable of effecting a very satisfactory sulphur reduction, about 45%, in naphthas of usual sul- Example III.A West Texas straight run petroleum distillate was passed in the vapor state at a temperature of 800 F. over a catalyst of 30-60 mesh zinc ore, the principal constituent of such ore being sphalerite.- After removal of the hydrogen sulphide formed in the decomposition of the organic sulphur compounds, the sulphur content of the treated product was 0.025 per cent as compared with 0.053 per cent on the untreated samplei While it is possible to operate this process in such a way that a completely sweetened gasoline is obtained as in Example I described above, it is not meant to be construed that such a product is always obtained in actual operation. The rate of conversion'of the organic sulphur comv pounds to hydrogen sulphide increases with both an increase in temperature and a longer contact time between the vapors and the catalytic material. Since these factors must always be taken into consideration, it is sometimes desirable to use such an extremely short time oi contact and/or such a low temperature that the resulting product is not entirely free of mercaptans altho a substantial sulphur reduction is obtained. 1 Having described the invention, what is claimed 1. The process of desulphurizing petroleum hydrocarbon fluid containing organic sulphur compounds as impurities, comprising heating the fluid in the vapor state to a temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature with a catalyst consisting of crude mineral ore containing a substantial proportion of a zinc compound, whereby the organic sulphur compounds are decomposed into hydrogen sulphide, and separating the hydrogen sulphide from the hydrocarbon fluid.

2. The process of desulphurizing petroleum oil with boiling point lower than the end point of kerosene, comprising vaporizing the oil, superheating the vapors containing organic sulphur compounds to a temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a zinc mineral catalyst, wherebythe organic sulphur compounds are decomposed into hydrogen sulphide, and separating the hydrogen sulphide from the oil.

3. The process of,desulphurizing gasoline containing organic sulphur compounds as impurities, comprising vaporizing the gasoline, superheating the vapors to a temperature within the range or about 600 to 800 F.; contacting the vapors for i e a period of about 2 to 10 seconds with a catalyst consisting of crude mineral ore containing a substantial proportion of a zinc compound, and separating the decomposed sulphur impurities from the gasoline.

4. The process of sweetening-gasoline containing mercaptans as impurities, comprising vaporizing the gasoline, superheating the vapors, to a temperature within the range of 600 to 800 F., contacting the vapors for a period of about 2 to 10 seconds with a catalyst consisting of crudemineral ore containing a substantial proportion of a zinc compound, whereby the mercaptans are decomposed into hydrogen sulphide, separating the hydrogen sulphide from the gasoline, and thereby obtaining a sweetened gasoline.

5. The process of desulphurizing petroleum oil containing organic sulphur compounds as impurities, said oil having a boiling point lower than the endpoint of kerosene, comprising vaporizing the oil, super-heating the vapors to a temperature within the range of 500 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a catalyst consisting of sphalerite ore, and separating the decomposed sulphur impurities from the oil.

6. In a process of desulphurizing gasoline in the vapor state, the steps which comprise superheating the vapors to a temperature within the range of about 600 to 800 F., contacting the vapors at substantially the same temperature for a period of about 2 to 10 seconds with a catalyst consisting of sphalerite ore, and separating the decomposed sulphur impurities from the gasoline.

7. The process of desulphurizing petroleum hydrocarbon gasescontaining organic sulphur compounds as impurities, comprising heating the gases to a temperature within the range of 500 to 800 F., contacting the gases at substantially the same temperature with a catalyst consisting of crude mineral ore containing a substantial proportion of a zinc compound, whereby the organic sulphur compounds are decomposed into hydrogen sulphide, and separating the hydrogen sulphide from the hydrocarbon gases.

ALBERT E. BUELL.

WALTER A. SCHULZE. 20 

